Lewis number (Le) is____________________?

Related Mcqs:

1. If mass diffusivity in a mixture is equal to the thermal diffusivity, then the Lewis number is____________________

   A. 0
   B. 1
   C. 1

2. Lewis number (Le) is___________________?

   A. Sc × Pr
   B. Pr × St
   C. Sh × Pr
   D. St × Sh

3. The value of Lewis number (Le = Sc/Pr) for air-water vapour system is around_________________?

   A. 1
   B. 0.24
   C. 3.97
   D. 600

4. Schmidt number and Lewis number for pure air at atmospheric conditions are respectively__________________?

   A. < 1 and ≈ 1
   B. 1 and 0
   C. > 1 and ≈ 1
   D. 0 and ≈ 1

5. Lewis number, which is important in problems involving simultaneous heat and mass transfer, is the ratio of__________________?

   A. Mass diffusivity to momentum diffusivity
   B. Thermal diffusivity to mass diffusivity
   C. Momentum diffusivity to thermal diffusivity
   D. None of these

6. For which of the following unit operations, Lewis number is of significance ?

   A. Adsorption
   B. Binary distillation
   C. Gas absorption
   D. Humidification

7. The operating cost of a distillation column at minimum reflux ratio is____________________?

   A. Minimum
   B. Maximum
   C. Infinite
   D. Zero

8. The most economical range of absorption factor is____________________?

   A. 0 to 0.5
   B. 0 to 3
   C. 1.25 to 2
   D. 5 to 15

9. Mass transfer co-efficient of liquid is____________________?

   A. Affected more by temperature than that for gases
   B. Affected much less by temperature than that for gases
   C. Not affected by the temperature
   D. None of these

10. If moisture content of solid on dry basis is X, then the same on wet basis is____________________?

    A. X/(X + 1)
    B. X/(1 – X)
    C. (1 + X)/X
    D. (1 – X)/X